1. Field of the Invention
The invention relates to a lid type vessel of a plastic material for laboratory use, specifically under conditions of an elevated temperature, e.g. in the PCR procedure.
2. Description of the Prior Art
Typically, lid type vessels of the aforementioned type have a filling capacity of a few millilitres or less than one millilitre.
Lid type vessels which are known comprise a vessel and a lid which has a lid bottom and a hollow cylinder on one side of the lid bottom, which either is inserted into a vessel opening like a stopper or is placed onto the vessel end having the vessel opening like a cap to provide sealing on the vessel outer wall. The lid may be formed separately from the vessel and may be joined thereto via a strap hinge.
In the lid type vessels which are known, the lid can become leaky or spring open when the pressure in the vessel rises beyond the ambient pressure. This can occur, for example, when specimens are being tempered in the lid type vessels. In particular, this problem is encountered during the polymerase chain reaction (PCR) during which specimens placed in the lid type vessels undergo treatment by means of so-called thermocyclers at elevated temperatures in order to multiply the DNA. The PCR comprises the three steps of denaturization at 94xc2x0 C., annealing at 40 to 60xc2x0 C., and DNA synthesis at 72xc2x0 C., which are repeated many times (mostly from 25 to 30 times).
If the (varying) pressure load leads to leakiness or causes the lid to spring open contamination might occur in other specimens or the laboratory environment.
Accordingly, it is the object of the invention to provide a lid type vessel which better protects the lid from leakiness and/or prevents it from springing open because of a pressure differential between the interior of the vessel and the environment.
The object of the invention is achieved by providing a lid type vessel of a plastic material for laboratory use, specifically in the PCR procedure, and including:
a tubular vessel which has a vessel bottom at one end and a vessel opening at the other end,
a lid which has a lid bottom and has at least one hollow cylinder on one side of the lid bottom, which is adapted to be inserted into a sealing seat at the vessel inner wall through the vessel opening, and/or which is adapted to be placed onto the end of the vessel having the vessel opening and in a sealing seat on the vessel outer wall, and
at least one axial portion of the hollow cylinder or vessel in the area of the sealing seat by means of which the hollow cylinder or vessel is alternately subdivided into harder and softer segments in a circumferential direction.
In the inventive lid type vessel, the sealing mates, i.e. the hollow cylinder of the lid and the vessel inner wall or vessel outer wall, bear on each other in the area of the sealing seat at a bias to achieve sealing. The hollow cylinder and the vessel are of a flexural strength which ensures that the lid is closed in a simple and safe manner with the sealing areas not undergoing any deformation preventing lid closure. In conventional lid type vessels, however, the circumferential sealing areas also are very rigid radially so that if there is an elevated pressure in the vessel no or hardly any intensification of the sealing action will be possible by widening the inner sealing mate. In contrast, in the inventive lid type vessels, since there are alternately harder and softer segments in the inner sealing mate, they cause the mate to be widened at least partially at an elevated pressure in the vessel, thus achieving an active intensification of the seal. Moreover, the pressure rising in the vessel increases the retention force acting in the sealing surface that keeps the lid to the lid to the vessel in spite of the intensified force acting on the lid bottom.
Another advantage over vessels having solid stoppers is that the cavity disposed directly below the vessel opening may be utilized as an expansion volume, e.g. when the specimen is being heated or shaken. Moreover, it becomes easier to close the lid as compared to conventional closures because of the softer segments if the allowance is the same between the lid and vessel. Further, working can be done at a smaller allowance if the lid type vessel is designed so as to cause the pressure in the vessel to sufficiently enhance the sealing action and retention force.
The aforementioned benefits also have an effect for a vessel for the cold treatment of specimens if the outer sealing mate is provided with the harder and softer segments because if the ambient pressure exceeds the pressure prevailing in the vessel it will be pressed more intensely against the internally located sealing mate.
According to an aspect, the axial portion of the hollow cylinder extends from the free end of the hollow cylinder or the axial portion of the vessel extends from the end of the vessel having the vessel opening, which helps achieve a particularly large expandability at the free end of the hollow cylinder or at the end of the vessel having the vessel opening, with a concurrent increase in the sealing action and retention force.
According to an aspect, also with a view to increasing the sealing action and retention force, the axial portion of the lid is extended up to the lid bottom or the axial portion of the vessel is extended at least over the whole covering area of the hollow cylinder of the lid placed on top.
According to an aspect, the harder and softer segments have borders which are parallel to the axis or are inclined towards the axis or engage each other. The borders which are parallel to the axis or are inclined towards the axis, in particular, have advantages in injection molding. If there are borders which are inclined towards the axis or engage each other the segments can be caused to get interlocked into each other constructionally, which can be an advantage while they are manufactured from different materials.
According to an aspect, the hollow cylinder or vessel has a soft material layer internally and/or externally, at least in the area of the axial portion.
According to an aspect, the hollow cylinder has a sealing bulge at the free end or the vessel has said bulge at the vessel opening. The bulge is apt to enhance the sealing action, specifically by an increase in surface pressure.
According to an aspect, the sealing bulge is softer than are the harder segments. As a result, the coefficient of friction may be increased specifically between the vessel and lid in order to intensify the retention force.
According to an aspect, the lid or vessel, at the proximal end of the axial portion, has at least one completely or partially circumferential annular portion which is softer than are the harder segments. The at least one annular portion is designed to enhance the radial expandability or compressibility of the axial portion, particularly if it extends along the base of the harder segments.
According to an aspect, the annular portion is arranged at the base of the hollow cylinder in the lid bottom and is softer than is the remaining lid bottom, also with a view to enhancing the radial expandability or compressibility of the axial portion. According to a further aspect, it is for the same reason that the lid bottom has radial portions which radiate outwardly from the annular portion and are also softer than is the remaining lid bottom.
According to an aspect, the softer regions (i.e. the softer segments and/or the sealing bulge and/or the annular portion and/or the radial portions) are comprised of the same material than are the adjacent harder regions (i.e. the harder segments and/or other regions of the lid or vessel) but, in contrast, are of a reduced wall thickness. Softness is increased here by a structural weakening of the materials in the regions concerned.
According to an aspect, the softer regions (i.e. the further segments and/or the sealing bulge and/or the annular portion and/or the radial portions) are comprised of a softer material than are the adjacent harder regions (i.e. the harder segments and/or other regions of the lid or vessel). Softness is increased here by employing softer materials. Softness can also be increased by combining a reduction in wall thickness and material use.
According to an aspect, the lid and/or vessel is/are made of the same soft material at any point within the softer regions and of the same harder material at any point outside said regions. The lid and/or vessel is/are then comprised of only two components.
According to an aspect, the harder material is polypropylene or polyethylene and/or the softer material is silicone or a thermoplastic elastomer or an elastomer or another soft polymeric material. In particular, plastic materials which have particularly good characteristics of adhesion to each other may be employed for the harder material and the softer material.
According to an aspect, the lid type vessel comprises at least two plastic material components of different moduli of elasticity. Preferably, the softer segments are made of a material the modulus of elasticity of which is lower by one or more powers of ten than is the modulus of elasticity of the material of which the harder segments are made.
The invention comprises forming the vessel and lid each from a separate component. The invention further comprises vessels and lids which are separate components adapted to be joined to each other, e.g. by means of a web which is integrally joined to one of the components and has a ring for being joined to the outer circumference of the other component. If formed separately, both the lid and vessel may be made completely or partially of the same plastic material or materials. However, they may also be comprised of different plastic materials or may be completely made of different plastic materials. The manufacturing techniques for the lid and vessel specifically include single-component and/or multi-component injection molding processes.
According to an aspect, both the lid and vessel are integrally manufactured in a single-component or multi-component injection molding process. Then, they may specifically comprise a film type hinge which joins the lid and vessel to each other. Likewise, however, this includes a possibility of releasably interconnecting the lid and vessel via a point of separation with the point of separation requiring to be undone to close the vessel.
According to an aspect, the lid is made of an elastic plastic material in its radius central area to provide self-acting sealing properties following a perforation, e.g. by means of a cannula for sampling purposes.